The present invention relates to data storage devices. More particularly, it relates to movement of rotary actuators for disc drives.
Typically, a disc drive includes an actuator arm with a magnetic read/write head for writing and reading data with respect to a track of a rotating disc. The actuator arm is arranged to turn on a pivot. The read/write head is located at one end portion of the actuator arm. The opposite end of the actuator arm generally acts as the rotor of an electric motor such as a voice coil motor.
Upon current being driven through the voice coil, the actuator arm rotates about the pivot thereby causing the magnetic head to move across the surface of the disc until it is positioned above a desired track in order that data may be written to or read from the track in question.
A voice coil is generally comprised of numerous components including a permanent magnet, coil, top pole, bottom pole, metal injection molding latch and latch bumper. The voice coil is typically assembled by means of adhesive and screws used to couple the components together. The number of components and the high degree of accuracy with which they must be positioned in order to properly assemble them together adds considerably to the overall expense of the finished product. Furthermore, a lengthy baking step is included in the production process to cure various epoxies or other adhesives used to assemble the prior art voice coil actuators. The baking step is undesirable as it is time-consuming, is a high consumer of energy and generates pollutant gases.
Attempts have been made to effect actuator movement through other arrangements so as to eliminate some of the disadvantages associated with conventional voice coil motors. For example, some have used a stator having a permanent magnet at an actuator pivot point, while magnetic coils on the actuator interact with the stator so as to move the actuator. Others have mounted magnets on a rotor so as to cooperate with a coil wound on an arcuate stator core at the actuator pivot.
These actuators have problems of their own. Because an air gap is required between the rotor and stator, and because the stator serves as a pivot point for the actuator, they typically impart undesirable pitch and roll torques to the actuator arm, which undermine the performance of the finished disc drive or require special design features to counteract them.
What the prior art has been lacking is an actuator drive which eliminates the problems associated with conventional voice coil motors while maintaining the rotational stability of these arrangements.
A preferred embodiment of the present invention is directed to a magnetless rotary actuator for carrying one or more read/write heads across a data bearing medium. The rotary actuator includes a stator and a rotor. The stator includes a plurality of independently controllable flux generating elements for directing flux towards the rotor, and the rotor includes discrete regions of low magnetic reluctance to interact with the flux generating elements. The actuator supports one or more read/write heads over the surface of a disc, and is pivotally mounted, so as to allow transmission of operative torque from the rotor to the read/write head(s).
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.